The present invention relates to a board-mounting device according to the preamble of the independent claim.
There has been known from EP 264 840 A2 a device of the described species which comprises two parts adapted to move one relative to the other. The first such part is a base carrier, adapted to be snapped down on the board, which comprises a predetermined number of detent legs provided with projections that engage behind the opposite side of the board in the mounted condition of the device. The base carrier comprises further locking elements that cooperate with the detent elements and are arranged in the second part which is configured as a device carrier. The locking elements of the device carrier may be arranged on bridges of the device carrier.
In their delivery condition, the two parts are fixed one relative to the other in a first locked position. Mounting is effected by applying a pressure on the device carrier in the direction of the board, whereby the detent legs pass and engage behind the bores in the board. The device carrier remains in the first locked position relative to the base carrier during that action. After mounting of the base carrier, the device carrier is then moved from the first into the second locked position and, thus, into its final mounting position, by application of a further pressure on the device carrier in the direction of the board.
The bridges of the device carrier may also be pushed through the bores in the board, which accommodate the detent legs in the mounted condition of the base carrier. This has the result that the bridges and the detent legs will be clamped one relative to the other.
The base carrier may be provided with wire bushings for guiding through connection wires of the devices that are pushed through corresponding bores as the two parts are pressed together.
Due to mechanical stresses to which the devices may be subjected during transport or other operations carried out in preparation of the assembly of the board, it cannot be excluded that the device carrier may get displaced from the first into the second locked position unintentionally. In this joined position, mounting the device is, however, no longer possible. Pushing the device carrier back from the second into the first position is of course possible in principle, In the context of an automated board mounting process, such a device will however be classified as defective.
Further, there may also arise situations during assembly where the device carrier is moved unintentionally from the first to the second locking condition. Any canting of the device relative to the board, for example, leads to higher forces being required for snapping down the base carrier on the board. Higher forces may be required for snapping the base carrier down on the board also if a burr should be encountered on the board, for example. The higher pressure which then has to be applied on the device carrier may cause the device carrier to be moved from the first to the second locked position unintentionally before the base carrier is snapped down on the board.